Solid-state image sensors in general comprise photodetector means for detecting radiation from the image and converting the radiation to charge carriers, and transfer means for carrying the charge carriers to an output circuit. One type of solid-state image sensor uses a CCD as both the photodetector and the transfer means. The solid-state image sensor generally includes a plurality of the CCD's arranged in spaced parallel relation to form an area array. One problem which has arisen in this type of solid-state image sensor is known as "blooming." Blooming is a phenomenon that occurs when the number of charge carriers generated in a photodetector site by the incident radiation exceeds the storage capacity of the site. These excess charge carriers then spill over or "bloom" into adjacent photodetector sites thereby degrading, and in some cases, completely obliterating the integrity of the image.
To overcome this problem various antiblooming structures have been developed and used in the solid-state image sensors. One structure which has been used is a vertical-overflow drain which comprises a drain extending into the substrate in which the image sensor is formed into which the excess charge carriers flow and from which they are carried away. Although these vertical-overflow drains do prevent blooming, they often result in degradation of other performance aspects of the image sensor. For example, they can result in photoresponse nonlinearity (or soft turn-on), and reduced quantum efficiency and well bounce. In addition, the vertical-overflow drain structures heretofore used require more complicated processing which results in higher sensitivity to process variations. Lateral-overflow drain (LOD) structures have also been used in solid-state image sensors. However, they have not been used extensively in image sensors in which a CCD serves as both the photodetector and the charge transfer means. This is because LOD structures used to date on these types of image sensors have been extremely hard to manufacture due to processing sensitivity, e.g., U.S. Pat. No. 4,593,303 to R. H. Dyck et al or European Patent No. 0,059,547 to H. Hosack et al.